Low-temperature fabrication of diamond-faced drilling bits

ABSTRACT

DIAMOND PARTICLES ARE SECURED TO A DRILLING BIT BODY BY A METAL LAYER DEPOSITED BY ELETROCASTING. MELT SPRAYING OF THE RESULTING BIT WITH MOLTEN METAL MAY BE ADDITIONALLY CARRIED OUT. THROUGHOUT THE PROCESS, THE DIAMOND PARTICLES ARE NOT   SUBJECTED TO TEMPERATURES EXCEEDING APPROXIMATELY 150*C., WHEREBY THEIR PROPERTIES ARE NOT IMPAIRED, AND HIGH DRILLING PERFORMANCE OF THE BIT IS AFFORDED.

United States Patent LOW-TEMPERATURE FABRICATION 01- DIAMOND-FACE!)DRILLING BITS 4 Claims, 14 Drawing Figs.

US. Cl 76/ 108,

51/309, 204/16 Int. Cl B2111 5/02 Field of Search 51/309;

[56] References Cited UNITED STATES PATENTS 2,147,843 2/1939 Jamar eta1. 51/309UX 2,360,798 10/1944 Seligman et al.... 5 l/309X 2,457,15612/1948 Jones 51/309 2,978,846 4/1961 Barron 51/309X 3,046,204 7/1962Barron 204/16 3,281,996 1 1/1966 Cuklanz 204/16X PrimaryExaminer-Bernard Stickney Attorney-Holman & Stern I ABSTRACT: Diamondparticles are secured to a drilling bit PATENTEDJUN28I971 3.587.358

sum 1 BF 3 x xxx INVENTOR. K. Ya; H l'lr o BYMMD PATENTEDJUNZBIHYI3,587,358

SHEET 2 OF 3 INVENTOR. S H l r a BY m, pm; v

PAT ENIEU JUN28 1971 3; S87 358 sum 3 OF 3 FIG. I3 FIG. l4

1 [i i Il'H Ill [1 l! I 1 g 1 I l I INVENTOR.

osuihro MM D HTTo/INEFS LOW-TEMPERATURE FABRICATION OF DIAMOND- FACEDDRILLING BITS BACKGROUND OF THE INVENTION This invention relates todrilling machinery for drilling holes in rock and other hard materialand more particularly to a new method for producing at low temperaturesdrilling bits faced with diamond of unimpaired properties, which bitshave high drilling performance.

Heretofore, a crown .or bit faced with diamond particles (bortz or bort)for drilling holes in rock and other hard layers has generally beenformed by pressing a large number of diamond particles into the innersurface of a casting mold for casting the bit and then pouring a moltenmetalsuch as an alloy or copper into the mold to form the bit. When amolten alloy at a temperature higher than 1,000 C. is poured in thismanner, however, it is difficult to avoid heat damage or to impairmentof the properties of the diamond particles, whereby the drillingperformance of the bit unavoidably drops.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a new and original method for fabricating diamond bits at lowtemperatures whereby the above-described difficulty is overcome, andwhereby the production of diamond bits of high drilling performance andthe sustaining of this high performance are made possible.

According to the present invention, briefly summarized, there isprovided a method for producing drilling bits faced with diamond ofunimpaired properties which is characterized by the steps of fabricatinga bit body having a working part and securing a large number of diamondparticles uniformly onto this working part by means of a metal layerdeposited by electrocasting with or without a further step of meltspraying of a molten metal onto the diamond facing thus formed.

The nature, principle, details, and utility of the invention will bemore clearly apparent from the following detailed description withrespect to preferred embodiments of the invention when read inconjunction with the accompanying drawings, in which'like parts aredesignated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view, in longitudinal section, of a bit body suitablefor supporting a crown mounted thereon according to the invention;

FIG. 2 is a bottom plan view of a cap suitable for use in accordancewith one example of the method of the invention;

FIG. 3 is an elevation, in vertical'section, showing one organization ofapparatus for carrying out the method of the invention with respect tothe bit body shown in FIG. 1 and with the use of the cap shown in FIG.2;

FIG. 4 is a side view showing the external appearance of a finisheddiamond-faced bit fabricated in the manner indicated in FIG. 3 accordingto the invention;

FIG. 5 is an elevation, in vertical section, showing one example of acrown mold suitable for use in another example of practice of theinvention;

FIG. 6 is a plan view of the mold shown in FIG. 5;

FIG. 7, 8, and 9, are elevations of the mold shown in FIG. 5 indicatingthree process steps in the fabrication of a crown;

FIG. 10 is a side view of a finished diamond crown fabricated by themethod and mold illustrated in FIGS. 5 through 9, inclusive;

FIG. 11 is a plan view of a bit body for still another example ofembodiment of the invention; 7

FIG. 12 is a relatively enlarged side view showing a single wire studfaced over approximately one-half thereof with diamond particles bondedthereto by metal plating;

FIG. 13 is a side view showing a bit body with a large number of wirestuds, each as shown in FIG. 12, imbedded in the working surfacethereof; and

FIG. 14 is a side view showing the external appearance of the bitillustrated in FIGS. 11, 12, and 13 in completed state.

DETAILED DESCRIPTION In one embodiment of the invention as illustratedin FIGS. 1 through 4, inclusive, a bit body having a tubular main part 1provided with a threaded part 2 for connection to a core barrel or drillstem (not shown) and a lower rim wall 3 of reduced wall thickness with awater-passage recess 4 of the shape shown in FIG. 1 is fabricated.

Separately, a synthetic resin cap 5 of annular shape which can be fittedover the above-mentioned lower rim wall 3 with a certain spacetherebetween is formed, and over the entire surface of this cap, a largenumber of small holes 6 are formed with uniform distribution as shown inFIG. 2.

Next, the surface parts of the bit body 1 other than the lower rim wall3 are covered by a method such as painting with a coating film 7 formasking or preventing metal plating. Thereafter, the cap 5 is fittedover the lower rim wall 3 in a manner to enclose a large number of finediamond particlesS within the aforementioned space therebetween.

The bit body 1, diamond particles 8, and cap 5 thus assembled are thenimmersed in the electrolyte of an electrocasting bath 9 as indicated inFIG. 3. Electrocasting is carried out by passing electric currentthrough the bit body and a nickel electrode plate 10 immersed in theelectrolyte above the bit body as electrodes, whereupon nickel ionsinfiltrate through the small holes 6 of the cap 5 and adhere to thelower rim wall 3 of the bit body 1 and to the fine diamond particles 8.The bit body I is then taken out of the electrocasting bath 9, and thecap 5 is removed therefrom, whereupon a diamond bit product as shown inFIG. 4 is obtained.

Thus, by the above-described method for producing diamond bits, only asmall number of process steps is necessary, and the process of fillingcertain parts by melt spraying of molten metal is not necessary. Thatis, by merely mass producing bit bodies and caps 5 respectively asillustrated in FIGS. 1 and 2, enclosing fine diamond panticles 8 withinthe space therebetween, carrying out electrocasting, and then removingthe caps, diamond bits of unimpaired properties can be readily andconveniently produced by only a low-temperature process step.

In another embodiment of the invention, use is made of a carbon mold 11as illustrated in FIGS. 5 and 6 which mold serves additionally as anelectrode in an electrocasting process described hereinafter. The mold111 is provided in its upper surface with an annular groove 12, at twoparts of which there are provided projections 13 for forming waterpassages of the bit crown.

This mold is used in the following manner to fabricate a bit crown.First, a large number of diamond bortz 14 are distributed and pressed asuniformly as possible against and into theinner surface of the annulargroove 12 as indicated in FIG. 7. Next, the mold 11 is immersed :in anelectrocasting bath (not shown), and an electrocasting process iscarried out between the mold I1 and nickel, whereupon a nickel coatinglayer 15 is formed within the annular groove 12 to cover the exposedsurfaces of the diamond particles 14 as indicated in FIG. 8.

Then a metal for melt spray coating such as a metal commonly referred toas metallikon" is sprayed in a molten state against the surface of thenickel coating layer shown in FIG. 8 thereby to fill the interior of thegroove with a melt sprayed metal layer 16 as indicated in FIG. 9. Thearticle thus formed and hardened in the state indicated in FIG. 10 andconstituting a bit facing crown is then taken out of the mold andsecured by silver brazing to the lower surface of a cylindrical bit body(not shown) having a flat end surface whereupon a finished diamond bitsimilar to that shown in FIG. 4 is obtained. It should be observed that,in fixing the crown facing to the bit body, a low-temperature methodmust be used.

In the above-described process steps, the electrocasting of course, is alow-temperature process. Furthermore, even when the molten metal in themelt spraying process is at a high temperature, the molten metalparticles blown by the spraying action against the coating layer surfaceof the diamond particles are at temperatures which do not exceedapproximately 150 C. Therefore, there is no possibility of the diamondparticles within the metal coating layer being subjected to damage or achange in properties.

Thus, since the diamond bit fabricated as described above in accordancewith the invention is subject to no heat damage or impairment ofproperties of its diamond particles as in some instances in known bits,its rock-drilling performance is high, and this high performance,moreover, can be positively and reliably sustained.

' In still another embodiment of the invention as illustrated in FIGS.ll through 14, inclusive, a bit body 17 has an annular bottom surface 18in which a large number of holes 19 are drilled in a uniformlydistributed pattern to receive and hold the root ends of correspondingwire studs 20. Each of the wire studs 20 made of steel (or an alloycontaining tungsten, nickel, molybdenum, and/or cobalt) has ametal-plated layer 21 covering the outer surface of approximatelyone-half thereof, the layer 21 serving to secure a large number ofdiamond bortz 22 to the wire stud 20 the bortz 22 being of still smallerparticle size than those used in the aforedescribed examples. These wirestuds 20 can be mass produced in the following manner.

The wire studs 20 are cut to equal lengths from a steel wire stock of adiameter suitable for fitting into the above-mentioned holes 19. A largenumber of the studs 20 thus cut are suspended vertically at the sameheight so that their lower halves are immersed in an electrocasting bath(not shown) containing a large number of diamond particles. Then, as thewire studs are thus suspended, metal plating (e.g., nickel plating)thereof is carried out, whereupon a large number of diamond faced wirestuds 20, each as illustrated in FIG. 12, can be mass producedsimultaneously.

The diamond-faced wire studs 20 thus produced are next fitted into andsecured in respective holes 19 in the bottom surface 18 of the bit body17, whereupon the bit assumes the state shown in FIG. 13.

Finally, a molten metal 23 such as metallikon" is sprayed onto the groupof wire studs, whereupon a completed bit as shown in FIG. 14 isobtained.

The step of securing the diamond particles to the wire studs 20 in theabove-described process according to the invention is a low-temperatureprocess. Furthermore, in the melt spraying of metal to obtain the bit inthe state shown in FIG. 14, the temperature imparted by the particles ofmolten metal to' the sprayed surface is of the order of C. as in theaforedescribed examples of the invention. Therefore, there is nopossibility of heat damage to the diamond particles or of change inproperties thereof.

An advantageous feature of the above-described organization of thediamond-faced bit is that, since the diamond particles are held in theaxial direction of the large number of wire studs, wear and reduction ofthe leading particles during drilling are immediately compensated for bythe successive participation in the drilling action of the followingparticles. Furthermore, labor such as that for brazing a molded bitcrown onto a bit body is unnecessary.

lclaim: v

1. A method for producing drilling bit crowns faced with diamond ofunimpaired properties, which comprises:

preparing a mold provided in its one surface with an annular groove, atleast one portion of which is provided with a projection to form waterpassage of the bit crown to be produced;

uniformly placing a large number of diamond particles against the innersurface of the annular groove; immersing the entire mold into anelectrocasting bath to conduct electrocasting between the mold and anickel electrode in the bath, the mold servirtg also as an oppositeelectrode to the nickel electrode in the electrocasting process, tosecure the diamond particles to each other by means of a metal coatinglayer formed within the annular groove by the electrocasting;

filling the interior of the annular groove structure with a metal toform a crown; and

extracting the crown from the mold.

2. The method as defined in claim 1, in which the mold is made of amaterial selected from the group consisting of carbon and a syntheticresin which is made electroconductive.

3. The method as defined in claim 1, in which the metal to fill in theinterior of the annular groove is a low melting point metal.

4. The method as defined in claim 1, in which the crown thus formed ismelt sprayed with a molten metal.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5 7,3Dat June 28. 197;

Invent0 Kunihiro Yoshino It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Cover Page,left-hand column, between lines 5 and 6, the following shouldbe inserted --[73] Assignee Kabushiki Kaisha Tone Boring, Tokyo, Japan--Signed and sealed this 11th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'I'SCHALK Attesting Officer ActingCommissioner of Patents 5 FORM PO-105O (10-697 USCOMM-DQ eoare. U 5GOVERNMENT PRINTING OFFICE \9'9 0-365-334

